1. Field of the Invention
The present invention relates to a color projector for displaying a color image with a single modulation panel.
2. Description of the Related Art
A color projector is a type of image display device for displaying color images. With a projector, light emitted from an illuminating optical system is modulated according to image signals with a modulation panel, such as a liquid crystal light valve, and the modulated light is projected onto a screen to obtain an image display. Because a modulation panel utilizes an electro-optical effect, the panel is also called an xe2x80x9celectro-optical device.xe2x80x9d
A typical color projector comprises three liquid crystal light valves to modulate a three-color (RGB) image. However, a drawback to a projector that makes use of three liquid crystal light valves is the complexity of the optical system structure. In view of this, there has been a need for the simplification of the structure of projectors.
Accordingly, an object of the present invention is to provide a projector having a simpler structure than the conventional ones.
In order to attain at least part of the above and other related objects, there is provided a projector for projection display of a color image. The projector comprises: a light source configured to emit illuminating light; a single modulation panel configured to modulate the illuminating light responsive to a given drive signal, thereby producing image light representing an image; a projection optical system configured to project the image light; a color filter mechanism, disposed in one of an incident-side path and an emergent-side optical path of the single modulation panel, for changing the illuminating light into one of a plurality of colors in a predetermined order; a converging optical system configured to converge the illuminating light on a filter surface of the color filter mechanism; and a controller configured to control the color filter mechanism and the single modulation panel. The color filter mechanism includes: a rotatable filter rotor having a plurality of color filters and a plurality of light-blocking mask bands provided at boundaries of the color filters; and a filter driver configured to rotate the filter rotor. The converging optical system converges the illuminating light such that a size of a spot of the illuminating light on the filter surface is smaller than the individual color filters.
The structure of this projector is simple because a color image can be projected and displayed by a single modulation panel. Also, since the size of the illuminating light spot on the filter surface is small, images of various colors can be stably displayed during a period in which the illuminating light spot is present on the various color filters.
According to an aspect of the present invention, the controller writes drive signals for color components corresponding to the plurality of color filters into the single modulation panel in synchronism with rotation of the filter rotor such that the drive signals for a next color component to be displayed are transferred to the single modulation panel during a specific panel rewriting period. The specific panel rewriting period includes at least part of a masked light passage period, the masked light passage period being a period during which a masked light portion, which is a portion of the illuminating light which passes through the mask bands, passes over the modulation execution region of the single modulation panel.
In this arrangement, it will be possible to reduce flickering of the image during the panel rewriting period.
It is also preferable if the panel rewriting period is set so as to substantially coincide with the masked light passage period.
This arrangement will also reduce flickering of the image during the panel rewriting period.
It is also preferable that an incident position of the illuminating light on the filter surface is set such that the masked light portion moves over the modulation execution region substantially vertically while covering at least one line of the single modulation panel. In this case, the controller may synchronize the rotation of the filter rotor and the transfer of the drive signals to the single modulation panel such that the drive signals for the next color component will be transferred to the at least one line of the single modulation panel covered by the masked light portion.
If the drive signal for the next color component is thus transferred to a line where the masked light portion is present, the color of the illuminating light that illuminates the various parts of the modulation execution region will correspond to the color component of the drive signal being written there, so it will be possible to reduce color deviation in the displayed image.
Also, the filter rotor may further include markings near the mask bands indicating positions of the mask bands, and he color filter mechanism may include a marking sensor for identifying the markings to produce marking detection signals. In this case, the controller may synchronize the rotation of the filter rotor and the transfer of the drive signals to the single modulation panel on the basis of the marking detection signals.
In this arrangement, it will be possible for the position of the modulation panel where the masked light portion is present to correspond well with the position where the drive signal is transferred.
Also, the plurality of color filters may include at least one color filter group made up of red, green, and blue color filters, and the markings may include a first type of markings indicating starting positions of the mask bands, and a second type of markings indicating an end position of the color filter group.
In this arrangement, it will be possible to recognize the start and end timing of the projection display of an image of various color components, and the start and end timing of the projection display of one frame of an image by one color filter group.